The invention relates to a hologram information forming method which can perform a natural stereoscopic display by using an electronic device and, more particularly, to a hologram information forming method for efficiently calculating a hologram phase distribution from a 3-dimensional structure and performing a stereoscopic display.
The stereoscopic display is means for enabling a depth or thickness structure of a 3-dimensional object to be easily visually understood and is strongly demanded in the display of a structure designed by a CAD or the like, the display of a medical image, or the like. A solid image is impressive as compared with the 2-dimensional display and is also used in a display for amusement or the like at amusement parks, movies, or the like.
Various kinds of methods have already been proposed with respect to the stereoscopic display. There is a hologram as means for enabling a solid image to be seen without attaching special glasses. The hologram is obtained by recording an object image onto a photographing dry plate by using an interference operation of the light. With regard to a still object, a color hologram having enough depth feeling has already been produced. However, in the recording to the photographing dry plate, it takes a time for a developing process and the display contents cannot be rewritten, so that the above means is inconvenient as a stereoscopic display system. In recent years, with the progress of a technique for realizing a high fineness of a liquid crystal display apparatus, an apparatus for electronically displaying a hologram by a liquid crystal display has been proposed (JP-A-64-84993). In case of electronically displaying a hologram by a liquid crystal display or the like, it is necessary to obtain a phase distribution of the hologram by calculations. The calculation of the phase distribution of the hologram is executed by product summing the phase contribution from respective points constructing a 3-dimensional object with respect to each point on the hologram.
On the other hand, there is a computer graphics (CG) method as a method for enabling a target having a 3-dimensional structure formed by a CAD or the like to be stereoscopically seen. The computer graphics is a technique such that 2-dimensional images when a target is seen from predetermined visual points are calculated and a stereoscopic feeling is really expressed in consideration of the reflection or shadow of the light. Since the computer graphics intends to display a 2-dimensional image, even when the observing position changes, only the same image is seen and a stereoscopic feeling is insufficient.
Hitherto, when a hologram phase distribution is calculated from the shape data of a 3-dimensional object, a 3-dimensional hidden line process is needed. Such a process corresponds to a technique for realizing a phenomenon that is peculiar to the stereoscopic observation such that an image can be seen by changing a visual point. However, in the hidden line process which permits that the visual point is freely changed in a 3-dimensional space, with respect to all of the points constructing a target, it is necessary to obtain a space distribution of the visual point at which each point can be seen and to obtain a calculating region of the phase distribution on the hologram and an amount of calculations in this instance is extremely large.
Specifically speaking, as shown in FIG. 1, when target objects 14 and 16 to be displayed in a space between a hologram plane 10 and a visual field 26 in which a stereoscopic display can be recognized, the calculation of the phase distribution regarding a point P on the hologram forming surface 10 is set as follows.
(I) When the point P of the target object 14 is seen from the visual field 26, a visual field portion 62 in which the P point can be seen and which is shown by a hatched region in which a visual field portion that is hidden by the object 16 existing on this side when the P point of the target object 14 is seen from the visual field 26 was eliminated is calculated.
(II) Subsequently, with respect to the visual field portion 62 in which the P point can be seen, a region of the hatched portion which crosses the hologram plane 10 that passes through the P point of the target object is obtained as a calculating region 60 of a phase distribution regarding the P point.
(III) The calculating region 60 is divided into micro regions and a phase distribution due to the light from the P point is calculated for each of the micro regions.
Since such calculations are executed with respect to all of the points of the target objects 14 and 16, an amount of calculations for them is extremely large. According to the processing speed of the present computer, it is difficult to calculate the phase distributions in a time which can be put into practical use as a display. It is a large subject to reduce such an extremely large amount of calculations.